The invention relates to curable topcoat compositions useable in multi-layered polymeric laminates, such as data carrying devices, and methods for using these compositions. The invention is also directed toward apparatus useful for preparing multi-layered polymeric laminates incorporating the topcoat compositions of the invention.
Polymeric multi-layered laminates, such as data carrying devices, are well-known and generally used for items such as identification cards, telephone calling cards, instant cash cards, credit cards, and company identification cards. Typically these types of laminates include a polymeric substrate (e.g., one or more polyester core layers) having multiple layers or films laminated thereon. Usually, the polymeric substrate is made from a rigid polymer sheet, and the multiple layers are made from flexible layers and/or films. In many of these types of processes, the films and/or layers are laminated into one multi-layered film and stored until the time that the multi-layered film is laminated to the polymeric substrate.
At least one of the films or layers in the multi-layered film can contain or can be a curable composition capable of enhancing a data carrying device's durability, strength and resistance to wear and tear. Typically, this composition is cured using, for example, ultraviolet radiation (i.e. UV). In general, the curable composition can be made from a composition containing a polymerizable monomer, a polymeric binder, a photoinitiator, and additives, such as colorants and plasticizers. Plasticizers generally facilitate processing and enhance the flexibility and toughness of the final product.
The curable composition, traditionally, is contained and laminated between two flexible sheets to form a multi-layered film. Flowability of the composition at room temperature while it is contained between sheets is important. If the composition has a relatively high flowability at room temperature or if the composition layer is too thick, then the composition tends to seep out from between the flexible sheets during storage. This seepage makes the multi-layered films more difficult to use, because the seepage can cause rolled films to stick together in spools, which creates difficulty in handling of the films prior to and during their use.
This problem is more fully discussed in U.S. Pat. No. 4,293,635, which issued on Oct. 6, 1981 to Flint et al. Flint et al. disclose a photopolymerizable composition that is used-in photoresist elements and that has reduced flowability at room temperature. The Flint et al. composition has a relatively high polymer to monomer ratio (i.e. more than about 2:1 parts by weight), which helps to reduce the composition's flowability at room temperature. However, this high ratio can add materials and processing costs to the final product. In addition, the requirement for a relatively thick (i.e. 0.003 cm) layer of the composition to be included in the photoresist element can increase processing cost and time.
In some processes, a curable composition is applied directly to a surface of a printed polymeric substrate instead of being sandwiched between sheets in a multi-layered film. One example of a process including the direct application of a UV curable composition to a substrate is disclosed in U.S. Pat. No. 5,302,438, which issued on Apr. 12, 1994 to Komamura et al. Komamura et al. disclose a method of preparing an image bearing recording member having a thermoplastic resin layer and radiation setting composition therein.
Another example of a process including the direct application of a UV curable composition to a substrate is disclosed in U.S. Pat. No. 5,254,525 which issued on Oct. 19, 1993 to Nakajima, et al. Nakajima et al. disclose an identification card that is coated with a UV setting resin and has a UV absorbing layer underneath the resin for image protection.
Direct application of the composition to the substrate requires more complex machinery than laminating a multi-layered film having the composition therein to the polymeric substrate. Thus, the Komamura et al. and Nakajima et al. processes seemingly require relatively complex equipment and skilled labor to prepare their image bearing recording member and identification card. These processes also require an operator to come into contact with chemicals that can be hazardous, which is not preferred for an office type of environment
In many conventional processes, one of the flexible sheets included in the multi-layered film is removed exposing the curable composition layer prior to laminating the film to the substrate. The multi-layered film minus a flexible sheet is then laminated to the substrate with the exposed curable composition layer laminated directly to a surface of the polymeric substrate. The polymeric substrate configured as a data carrying device for example, can have print matter on one or more of its surfaces--including the surface laminated directly to the curable composition layer.
If the device is a card, the printed matter generally identifies the cardholder and/or the type of card. The printed matter can be applied using dye diffusion or thermal transfer printing methods known in the art. Once the printed matter is applied, it is important that the printed matter not smudge, deteriorate or crack during the useful life of the data carrying device. It has been discovered that plasticizers included in the curable composition layer, which is laminated directly to a printed surface of the polymeric substrate, can attack and degrade the printed matter on the polymeric substrate. This degradation reduces the useful life of the data carrying device. It has been discovered that thermal transfer printed and dye diffusion printed surfaces are especially susceptible to this attack and degradation.
It is desirable to prepare a stable and durable data carrying device that has improved physical properties, such as plasticizer or chemical resistance, adhesion, abrasion resistance and/or flexibility. It is also desirable that these devices be capable of being prepared by an unskilled end user in an office environment using office-size equipment. Furthermore, it is desirable that the equipment operator not have significant exposure to hazardous chemicals.